Previous studies involving the determination of residual aluminum in Antihemophilic Factor (Human) (AHF) by Graphite Furnace Atomic Absorption Spectrometry (GFAAS) have emphasized direct analysis with minimal sample pretreatment. Pretreatment generally involved sample dilution with the addition of matrix modifiers such as sulfuric acid and the non-ionic detergent Triton X-100 immediately prior to analysis. A traditional approach commonly used for pretreatment is open vessel wet digestion of sample with a concentrated acid using an external heat source. This approach has not been applied to the present study mainly because of the extended length of time required to effect a complete digestion of sample, the possibility of analyte loss during the digestion and the probability of environmental or cross contamination of sample. A modified approach currently under investigation employs wet acid digestion of sample using microwave energy as a heat source. The microwave approach combines rapid microwave heating of acids under pressure to dramatically reduce digestion time. Digestions are performed in closed container Teflon PFA vessels thereby minimizing extraction of contaminates from the vessel wall. Since airborne particles cannot enter a sealed vessel extraneous contamination is eliminated. As in earlier studies, method validation is being primarily accomplished by determining the aluminum content of U.S. Standard, Aluminum in 5% Albumin, Lot #1. The aluminum content of this intralaboratory reference material has been previously determined by the National Institute of Standards and Technology using three independent analytical methods.